Method of determining the oxygen content of copper



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TELLuR/UM c. M, ANDERSON 4Err AL Filed my 19, 1945 THF@ wmu METHOD OFDETERMINING THE OXYGEN CONTENT 0F' COPPER April 10, 1951 w. M/ mmmwm Newm @MLM MM40. f Raw Patented Apr. 10, 1951 UNITED STATES PATENT OFFICE vMETHOD OF DETERMINING THE OXYGEN CONTENT OF COPPER Carl M. Anderson,Chicago, Robert A. Harris, Oak Park, and Charles C. Patton, Chicago,Ill., assignors to Western Electric Company, Incorporated, New York, N.Y.

York

, a corporation of New Application July 19, 1945, Serial No. 605,950

3 Claims. (Cl. 23-230) This invention relatesto a method of determiningthe oxygen content of copper. l

In the manufacture of some articles from copper, it becomes necessary tobraze or treat the articles in a reducing atmosphere as a step incidentto the manufacture of the articles. In such articles, the presence ofeven very small quantities of oxygen in the copper cause warping of thecopper parts and, as a consequence of this distortion, the articles aredefective. Accordingly, it has become of primary importance to determinethe purity of copper to be used in such processes.

It is an object of the present invention to provide a method ofdetermining oxygen in the copper.

In accordance'with one embodiment of the invention, a sample of copperis heated in a hydrogen atmosphere or a reducing atmosphere containing arelatively large amount of hydrogen and then cooled in the sameatmosphere. Prior to heating the sample, it is measured to determine itsdiameter and, after the heating and cooling in the reducing atmosphere,it is again measured. ItV has been found that copper containing oxygenwill grow when heated to elevated temperatures in the presence ofhydrogen, apparently due to the formation of voids at the grainboundaries when the oxygen and hydrogen y combine.

A complete understanding of the invention may be had'by reference to thefollowing detailed description when considered in conjunction with theaccompanying drawing, wherein the single gure illustrates graphicallythe percent oi in-y crease in diameter of various commercial brands ofpure copper when treated in accordance with the present invention. f

In accordance with theY present invention, copper rods of from assmallras .25" in diameter to as large as approximately .8 in diameterand just under one inch long are heated to' an elevated temperature inthe presence of either pure hydrogen or a gas such as ammo gascontaining '75% H2, 25% N at temperatures from'1550" F. to1850 F. andthen are cooled in the same atmosphere, whereupon a comparison of thediameter ofthe samples prior to and after heat treat- 'ing' willindicate whether or not there is oxygen at the grain boundariesand'probably some of it escapes as steam, leaving voids at theboundaries. The combining of thehydrogen and oxygen at these hightemperatures will form steam which requires more space than the oxides,thus leaving the voids and increasing the overall dimensions of thesample.

Examination of copper treated in this manner when a microsection isexamined at a suitable magnication, such as 75X, shows voids at the vgrain boundaries, which probably-accountsfor Commercial electrolyticcopper, known as` I tough pitch copper, is known to contain fromapproximately .03% to approximately .05% of cuprous oxide and for mostmanufacturing purposes, Where a high degree of conductivity is required,copper containing -a maximum of .07% of oxygen is acceptable. However,in the manufacture of some parts which are later to be treated in areducing atmosphere, the amount of oxygen in commercially pure orelectrolytic copper is too great and the parts to be manufactured becomeembrittled and warped, whereas the material known as oxygen-free highconductivity copper is suiliciently low in its oxygen content so that nodeleterious embrittlement or warping will occur when parts made fromthis vmaterial are treated in reducing atmospheres,

the dimensional growthofthe samples. It has been further noticed inthecourse of experiments that the diameter of a rod exhibits a vmuchgreater tendency Yto growithan a comparable length of rod. Thisapparently has resulted from'the distortion of the grain structure inthe formation of the rod, thus providing more boundaries in thecross-sectional area of the rod Yfor a given dimension than in thelength of the phorous deoxidized copper containing a small amount oftellurium, andthe product known asV tested. The samples tested indicatedthat growth occurs when there is oxygen present in the samples.

As indicated in the drawing, the percent increase in diameter of; toughpitch copper, when treated at temperatures ranging from 1550 F. to 1850F. in atmospheres containing principally hydrogen, gradually increasesfrom approximately 1.29% to approximately 2.04%. This apparentlyindicates that as the treating temperature is raised, the amount ofexpansion or growth of the sample increases progressively. However,there is a limit to the temperature which may be used since somewherej-ust above 1850 the copper becomes so plastic as it approaches themolten stage that the measurement oi it would not be accurate. Thesamples of tough pitch copper tested were approximately- 1/2" indiameter and almost one inch in length and their growth in diameterfollowed the line l.

A number of phosphorous deoxidized copper samples having some telluriumin them were tested under the same temperature and atmosphericconditions and they Yexhibited a growth from where their percentage ofincrease in diameter, after heat treatment, and cooling, ranged from.458% at 15.50 F. to 1.65% at 1850 F., as indicated by the line 2. Anumber of samples of oxygen-free high conductivity copper oontaining asmall amount of tellurium changed in diameter from an increase of from.04% at 1550 F. to a maximum of .128% at. 185.0 F., as indicated by theline 5.

In tests where the same conditions were.. maintained, a number ofsamplesy of oxygen-free high conductivity copper treated at 1550 F.,160'?e 1650 F., 1750 F., and 1850 F. were measured and three of thesamples, as indicated by the encircled dots at. 3, apparently shrunk,whereas four samples, as indicated by the. encircled dots 4, apparentlymaintained exactly the same diameter. This is believed to indicate thatthe oxygen-free high conductivity copper did not grow in size and,inasmuch as the, three samples which apparently shrunk are within therange of accuracy of the measurements made, it. is safe. to assume thatthere will be no Change in size of copper samples which are free fromoxygen when the copper is treated at. the ele.-

vated temperatures in a hydrogen atmosphere and it, is also believed tobe iair to, assumer that a. Small amount of oxygen in Copper will causethe copper tov increase in size, when treated as described hereinbeiore.When the copper increases in diameter less than .20%, it is acceptableand does not warp or become embrittled to a detectable extent when usedin the manufacture of electrical apparatus which is later treated inahydrogen atmosphere.

What is claimed is:

1. The method of determining the deleterious effect of the oxygencontent of copper which comprises determining the dimensions of a sampleof copper, heating said sample to from approximately 1550 F. toapproximately 1850 F. for from fteen to twenty minutes, cooling thesample to room temperature, maintaining a hydrogen atmosphere around thesample during the heating and cooling, and then again determining saiddimensions to indicate variations in said measurement above and below.20% of the original dimensions.

2. The method of grading various samples of coppers in cylindrical formby determining the deleterious eiect of the oxygen content in eachsample, which comprises determining the diameter of each sample ofcopper, heating each sample to from approximately 1550 F. toapproximately 1850" F. for from fifteen to twenty minutes, cooling eachsample to room temperature, maintaining a hydrogen atmosphere aroundeach sample during the heating and cooling, and then again determiningsaid diameters to ascertain whether the percent increase in diameter foreach sample falls below a predetermined value.

3. The method of grading coppers by determining the deleterious effectof the oxygen content in various samples of the. coppers, whichcomprises determining a particular dimension of each sample of copper,heating each of said samples to a predetermined temperature within therange of 1550 F. to approximately 1850 F. for from fteen to twentyminutes, cooling each sample to room temperature, maintaining a reducingatmosphere Vcontaining hydrogen around each sample during the heatingand cooling, and then again determining said dimension of eachindividual sample to ascertain the percent change in size relative to apredetermined value to determine the grading of each sample.

CARL M. ANDERSON. ROBERT A. HARRIS. CHARLES C. PATTON.

REFERENCES CITED The following references are of record in the le ofthis patent:

N.l B. Pilling, Action of Reducing Gases on Hot Solid Copper, Trans. A.I. M. E. 1919, vol. 60, p. 3.22.

Metals Handbook, American Society for Metals, 1939, Cleveland, Qhio, p.1391.

Rhines et al., Trans. A. I, M, E., vol. 143, 1941, pages S12-325.

1. THE METHOD OF DETERMINING THE DELETERIOUS EFFECT OF THE OXYGENCONTENT OF COPPER WHICH COMPRISES DETERMINING THE DIMENSIONS OF A SAMPLEOF COPPER, HEATING SAID SAMPLE TO FROM APPROXIMATELY 1550* F. TOAPPROXIMATELY 1850* F. FOR FROM FIFTEEN TO TWENTY MINUTES, COOLING THESAMPLE TO ROOM TEMPERATURE, MAINTAINING A HYDROGEN ATMOSPHERE AROUND THESAMPLE DURING THE HEATING AND COOLING, AND THEN AGAIN DETERMINING SAIDDIMENSIONS TO INDICATE VARIATIONS IN SAID MEASUREMENT ABOVE AND BELOW20% OF THE ORIGINAL DIMENSIONS.